1. Field of the Invention
The field of the present invention generally relates to mounting systems and, more particularly, to solar mounting systems for mounting photovoltaic modules or panels on generally flat surfaces such as, for example, low-sloped building rooftops, or the like.
2. Background
There is a need for a commercial low-sloped roof mounting system that merges the functionality of both modular and rail based systems, combining the advantages of each without the drawbacks. Modular mounting systems are quick to install, can have low part count, low shipping cost, have a low cost of manufacturing, flow with roof undulations and around obstructions, can have standardized engineering that adapts to layout changes, and can have superior thermal compensation. However, modular systems on the market do not have superior performance in wind and seismic situations. Specifically, modular systems have low structural rigidity and therefore low load sharing (i.e., effective load area), which increases the weight required to resist wind loads and increases the attachments required in high wind locations. Lack of interconnection also increases the number of attachments required to resist seismic forces. Rail-based systems perform well in wind and seismic performance, but are inferior to modular systems in all other aspects noted above. The ideal system is one that is a hybrid of modular and rail-based systems, one that has low part count and installs in a modular way, but once installed is structurally connected to perform like a rail-based system.
The design challenges to accomplish this hybrid system are mainly dealing with roof undulations and thermal compensation, which are challenges to rail-based systems. Roof undulations are common in low-sloped roofs which can vary in tilt up to 5 degrees to allow for drainage. To deal with roof undulations, the system should flow with the roof in all directions. The challenge is to allow for the system to be installed on uneven surfaces, yet lock the system in place once installed so that it acts as one structural unit. A conflicting requirement with locking the system in place permanently once installed is that the system must also be able to expand and contract with temperature fluctuations. As such, what is needed is a hybrid mounting system for photovoltaic modules that meets the requirements set forth above.
There is also a need for a photovoltaic mounting system with improved ballasting. Standard construction concrete blocks are most commonly used to ballast low sloped photovoltaic (PV) arrays. The problems with this method include cost to manufacture, cost to deploy, longevity, and environmental impact. Concrete blocks have a substantial cost to manufacture and deploy. Some estimate that the cost of material and installation of these blocks add $0.03-$0.04/watt to solar installations, which is 20% of the mounting system cost. Also, concrete blocks may degrade over the 25 year life of the solar system, cracking and disintegrating has been observed. This results in decreased effectiveness of the blocks and creates unwanted deposits on the roof surface. Also, concrete has high embedded energy in the production of cement, a main component. There are some systems on the market that have custom concrete blocks integrated into the system. While these solutions reduce the time and cost required to deploy the blocks, they still have issues of cost to manufacture, longevity concerns, and environmental impact.
Thus, what is needed is a mounting system that obviates the need for concrete ballast blocks to avoid all the issues with concrete blocks discussed above. This can be accomplished by either removing the need for weight altogether (adding structural rigidity, improving aerodynamics, etc.) and/or ballasting with another source of weight. While gravel has been used in solar mounting systems, these systems require installers to buy gravel separately, deliver gravel onto the roof, and fill up containers integrated into the racking system with gravel, all of which are not desirable for installers.
Moreover, there is a need for a photovoltaic mounting system with effective passive means by which to tilt or rotate the photovoltaic modules in the array. In a conventional photovoltaic array, the photovoltaic modules are tilted towards the sun to maximize solar gain, but this tilt increases the wind load and corresponding ballast required to hold modules down. Therefore, the mounting system typically requires ballast and structure to counteract negative wind pressure. Also, snow can build up on the modules. Snow reduces solar gain in the winter and increases the amount of structure needed to support a module.
As such, what is needed is a mounting system that passively changes the module tilt based on the environmental forces. In a wind event, the module would ideally be flat and high off the roof to allow for pressure equalization. In a snow event, the module would have a high tilt to shed snow.
Furthermore, there is a need for a photovoltaic mounting system with simple passive means for tilting or rotating the photovoltaic (PV) modules in the array towards the sun, rather than the employing a complicated active system, such as those on the market today. While tracking systems (i.e., PV mounting systems that follow the sun) are desirable because they increase the amount of electricity produced per panel, their drawbacks typically outweigh this benefit. One drawback is that they are cost prohibitive, comprised of many higher cost components. Also maintenance is required to ensure continual operations, which is costly over the 25 year lifespan of a PV system. As such, there is a need for a PV tracking system that uses fewer low cost components so as to reduce the cost of the system, and requires virtually no maintenance.